Find force link 3 exerts on link 2

1. The problem statement, all variables and given/known data
A chain consisting of five links, each of mass 0.105 kg, is lifted vertically with a constant acceleration of a = 3.5 m/s2. Find the magnitude of the force that link 3 exerts on link 2.

1. The problem statement, all variables and given/known data
A chain consisting of five links, each of mass 0.105 kg, is lifted vertically with a constant acceleration of a = 3.5 m/s2. Find the magnitude of the force that link 3 exerts on link 2.

where FU is the force pulling up, (0.105*3) is the mass of the link's 5, 4, and 3 weighing down on link 2 (mg=weight) and then the mass*accel on the other side.

This is wrong. why? and how do i get the right answer?

It looks like your calculation and answer is correct, although you left out a 3 in an apparent typo omission (see above in red). Unless, the links are numbered 1 thru 5 bottom to top, rather than 1 thru 5 top to bottom??